Liquid level sensing apparatus and related methods

ABSTRACT

Liquid level sensing apparatus and related methods are disclosed. An example method includes moving a cannula to pierce a seal of a container to provide access to a liquid in a cavity of the container; moving a probe through a passageway of the cannula and into the cavity of the container; and when the probe is at least partially positioned in the cannula: providing a first signal to the probe to cause the probe to emit a first electrical field; and providing a second signal to the cannula to cause the cannula to emit a second electrical field.

CROSS-REFERENCE TO RELATED APPLICATION

This patent arises from a continuation application of U.S. patentapplication Ser. No. 15/629,495 filed on Jun. 21, 2017, (now U.S.Patent), which claims the benefit of U.S. Provisional Patent ApplicationNo. 62/353,461, filed Jun. 22, 2016. U.S. patent application Ser. No.15/629,495 and U.S. Provisional Patent Application No. 62/353,461 arehereby incorporated herein by reference in their entireties.

FIELD OF THE DISCLOSURE

This disclosure relates generally to liquid level sensing systems, and,more particularly, to liquid level sensing apparatus and relatedmethods.

BACKGROUND

Clinical chemistry and immunoassay diagnostics provide automatedanalyzers for processing biological fluids. Automated clinical analyzersprovide rapid results with relatively high accuracy. To automateclinical chemistry and immunoassay diagnostics, analyzer systems oftenemploy liquid sensing methods to aspirate a sample fluid from acontainer or test tube.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example automated analytical apparatus that may beimplemented with an example liquid level sensing apparatus and relatedmethods in accordance with the teachings of this disclosure.

FIG. 2 illustrates a top plan view of a portion of the automatedanalytical apparatus illustrated example pipette system implemented withthe example liquid level sensing apparatus and related methods disclosedherein.

FIG. 3 is a block diagram of an example liquid level sensing apparatusin accordance with the teachings of this disclosure.

FIG. 4 is a schematic illustration of the example liquid level sensingapparatus of FIG. 3.

FIGS. 5-8 illustrate schematic illustrations of the example liquid levelsensing apparatus of FIGS. 2-4 at various stages of operation.

FIG. 9 is a flowchart representative of an example method ofimplementing the example liquid level sensing apparatus of FIGS. 3-8.

FIG. 10 is a block diagram of an example processor platform capable ofexecuting the instructions of FIG. 9 implementation of the liquid levelsensing apparatus of FIG. 3.

The figures are not to scale. Instead, to clarify multiple layers andregions, the thickness of the layers may be enlarged in the drawings.Wherever possible, the same reference numbers will be used throughoutthe drawing(s) and accompanying written description to refer to the sameor like parts.

DETAILED DESCRIPTION

Automated analytical apparatus (e.g., clinical chemistry and/orimmunoassay diagnostic analyzers) rely on liquid level sensing toautomate processing or testing of fluids (e.g., a biological fluid orsample), reagent liquids and/or buffer liquids contained or stored incontainers or tubes. For example, detecting the presence of the liquidand/or locating a surface of the liquid permits controlled emersion of apipetting apparatus into the liquid to enable a consistent amount ofliquid volume to be aspirated or removed from a container. For example,known clinical analyzers typically employ liquid level sensing for usewith open, uncapped containers. When an open, uncapped container isemployed, a pipetting probe of the clinical analyzer may be positionedwithin the open-end container and a volume of the sample fluid may beaspirated or removed from the container.

Example liquid level sensing systems disclosed herein provide apipetting system employing automated liquid level sensing capability.Specifically, example liquid level sensing systems disclosed herein maybe used with automated analytical apparatus employing either open-endcontainers and/or closed or capped containers. Example liquid levelsensing systems disclosed herein may include a pipetting systememploying a pipetting probe to aspirate a liquid from a container and acannula to pierce a septum or cap (e.g., a cover or top) of a container.In some examples, example pipetting systems disclosed herein enable aconsistent amount of liquid volume to be aspirated or removed from acontainer. To detect the presence of the liquid and/or an amount ordistance of emersion of the pipetting probe into the liquid, exampleliquid level sensing apparatus disclosed herein may be configured toemit or transmit a signal (e.g., a radio frequency signal) toward anantenna positioned adjacent the container.

In particular, to detect a liquid level of a container, example liquidlevel sensing apparatus disclosed herein may cause the pipetting probeto transmit a first signal. Additionally, to prevent the piercingcannula from degrading and/or otherwise interfering with a signaltransmitted by the pipetting probe during level sense operation (e.g.,when the pipetting probe is moving toward a liquid in a container), anexample cannula disclosed herein may be configured to transmit a secondsignal. In some examples, the first signal is substantially the same(e.g., identical) to the second signal. In some examples, the firstsignal is different than, or phase-shift controlled relative to, thesecond signal. In some examples, the first signal and/or the secondsignal may have a frequency between approximately 0.3 Hz and 300 GHz. insome examples, the first signal and/or the second signal may be adigital signal and/or any other type of signal. For example, the firstsignal and/or the second signal may be digital pulse signal and/or anyother type of signal modulation. In some examples, the first signaland/or the second signal may have a frequency between approximately a DCpotential and 300 GHz.

In some examples, example liquid level sensing systems disclosed hereinmay include a phase-lock loop (e.g., an analog phase-lock loop, adigital phase-lock loop, etc.) for frequency generation, improvedfrequency stability and alignment (e.g., to maintain a relationship suchas a phase-shift relationship, an equivalent relationship) between thefirst signal and the second signal. Thus, a phase-lock loop controlsystem may be employed for signal phase integrity and/or noise andjitter control.

Example liquid level sensing systems disclosed herein electricallyenergize a cannula and the pipetting probe with electrically phasecontrolled signals. For example, a signal source (e.g., an oscillator)may provide electrically in-phase signals (e.g., the same signals orfrequency, or a signal or frequency having a predetermined phase shift)to the cannula and the pipetting probe so that the pipetting probe andthe cannula emit signals that are substantially the same or controlled(e.g. via phase shift).

In this manner, the pipetting probe and/or the piercing cannula may becomposed of an electrically conductive material (e.g., a metallicmaterial) to enable repeated piercing of containers without causingdamage the cannula and without the cannula interfering or degrading thesignal emitted by the pipetting probe when the pipetting probe isdisposed in a container to detect a level of a liquid. As a result, theenergized piercing cannula disclosed herein may puncture (e.g.,vertically puncture) a top or cap of a closed container and theenergized pipetting probe may be positioned through a channel or openingof the energized piercing cannula at similar or equal electricalpotential (e.g., electrically phase controlled) without electricalimpediment of the signal transmitted by the pipetting probe as thepipetting probe makes coordinated contact with liquid in the container.

An antenna (e.g. a transmitting or receiving antenna) may be positionednear or adjacent the container to receive or transmit the detectedsignal transmitted by the pipetting probe and/or the cannula, which maybe analyzed for indication of contact with liquid in the container. Insome examples, if the signal emitted by the cannula is phase controlled(e.g., radiates a frequency or signal having a phase shift) compared tothe signal emitted by the probe, the antenna and/or a signal analyzermay be configured to differentiate (e.g., filter) the signal emitted bythe probe and the signal emitted by the cannula. In addition, exampleliquid sensing systems disclosed herein maintain integrity of liquidlevel sensed during a descent of an electrically conductive pipettingprobe through an electrically conductive piercing cannula that haspierced a closed or capped container. In some examples, an examplepiercing cannula disclosed herein may be energized using a wire to carrythe signal (e.g., a radio frequency signal) from, for example, a signalsource (e.g., a signal generator, a printed circuit board, etc.) to thepiercing cannula. In some examples, the piercing cannula is energizedusing capacitive coupling to provide a connection between the signalsource, the piercing cannula and/or the probe.

FIG. 1 is an example automated analytical apparatus (e.g., animmunoassay analytical system) in accordance with the teachings of thisdisclosure. The analytical system 100 of the illustrated exampleprovides an automated continuous and/or random access analytical system,capable of simultaneously effecting multiple assays of a plurality ofliquid samples. The analytical system 100 of the illustrated exampleincludes a user input or interface to enable a user and/or other controlsystem to input information or commands to the analytical system 100. Insome examples, the example liquid level sensing apparatus disclosedherein may be retrofitted with existing analytical systems employed inthe field. For example, the liquid level sensing apparatus disclosedherein may retrofit a system disclosed in U.S. Pat. No. 5,627,522, whichis incorporated herein by reference in its entirety.

FIG. 2 is plan view of the analytical system 100 of FIG. 1. The exampleanalytical system 100 of the illustrated example employs a pipettingsystem 200 (e.g., a robotic arm pipetting system) employing an exampleliquid level system in accordance with the teachings of this disclosure.The pipetting system 200 obtains fluid from containers 202 held by arotating carousel 204. The containers 202 may include sample containers,reagent containers, and/or any other container. The containers 202 ofthe illustrated example may include a (e.g., pierceable) septum or cover206 that covers an opening of the containers 202 (e.g., caps, lids,etc.). The example analytical system 100 of FIGS. 1 and 2 includes afirst carousel 208 that is serviced by a first pipetting system 210 anda second carousel 212 that is serviced by a second pipetting system 214.The first pipetting system 210 and/or the second pipetting system 214may employ the example liquid sensing system disclosed herein. To move(e.g., aspirate or deliver) fluids relative to the containers 202, thefirst pipetting system 210 and the second pipetting system 214 include adrive system 216. The drive system 216 of the illustrated exampleincludes a translatable arm or guide 218 to move a probe or cannularelative to the containers 202 positioned in the first carousel 208 orthe second carousel 212 in a first direction 220 (e.g., a horizontaldirection) and a second direction 222 (e.g. a vertical direction, whichwould be into and out of the paper or screen in the orientation shown inFIG. 2) that is different than the first direction 220 in theorientation of FIG. 2. For example, the translatable arm or guide 218may include a first telescopically extending arm to move the cannulaand/or the probe in the first direction 220 relative to the containers202, a second telescopically extending arm to move the cannula in thesecond direction 222, and a third telescopically extending arm (e.g.,slidable within the second telescopically extending arm) to move theprobe in the second direction 222. The third telescopically extendingarm may be configured to move the probe independently of the secondtelescopically extending arm of the cannula.

FIG. 3 is a block diagram of an example pipetting system 301 implementedwith an example liquid level sensing system 300 in accordance with theteachings of this disclosure. For example, the example pipetting system301 and/or the liquid level sensing system 300 of the illustratedexample may be used to implement the first pipetting system 104 and/orthe second pipetting system 106 of the example analytical system 100 ofFIGS. 1 and 2. It is to be understood that the liquid level sensingsystem 300 of the present invention can be utilized in any automatedinstrument where liquid level sensing is desired

The pipetting system 301 of the illustrated example includes a pipettingprobe 302 and a piercing cannula 304 that are movable relative to acontainer 306 (e.g., the container 202 of FIG. 2) via a drive system 308(e.g., the drive system 216 of FIG. 2). For example, the pipetting probe302 of the illustrated example transfers fluid to and/or from thecontainer 306 (generically representing a container in a reactionvessel, a reagent pack, or a test container). In some examples, thecontainer 306 may be supported by a holder 310. The container 306 maybe, for example, a test tube or other containers having a closed endprovided by, for example, a cap (e.g. having a septum). The piercingcannula 304 pierces or provides an access opening to a closed end of thecontainer 306 to enable the pipetting probe 302 to be inserted in acavity of the container 306. More specifically, the pipetting probe 302passes through a passageway of the piercing cannula 304 to access thecontainer 306.

The drive system 308 of the illustrated example includes a probepositioner 312, a first motor 314, a cannula positioner 316 and a secondmotor 318. The probe positioner 312 moves the pipetting probe 302relative to the cannula 304 and/or the container 306 via the first motor314. For example, the probe positioner 312 moves the pipetting probe 302relative to the cannula 304 and/or the container 306 in the firstdirection (e.g., the vertical or up and down direction relative to anupper surface or cap of the container 306) and the second direction(e.g., the sideways or horizontal direction relative to an upper surfaceor cap of the container 306) different than the first direction. Thecannula positioner 316 moves the piercing cannula 304 relative to thecontainer 306 via the second motor 318. For example, the cannulapositioner 316 moves the cannula 304 relative to the container 306 in afirst direction (e.g., a vertical or up and down direction relative toan upper surface or cap of the container 306) and a second direction(e.g., a sideways or horizontal direction relative to an upper surfaceor cap of the container 306). The probe positioner 312 and/or thecannula positioner 316 may include a telescopically movable robotic arm(e.g., the guide 218 of FIG. 2) to move the pipetting probe 302 and/orthe cannula 304 in the first direction and a telescopically extendingarm to move the pipetting probe 302 and/or the cannula 304 in the seconddirection. In some examples, the probe positioner 312 is a dedicatedtelescoping arm that moves independently from the cannula positioner316. In this manner, the probe positioner 312 can move the pipettingprobe 302 in the first direction and/or the second direction relative tothe cannula 304, and the cannula positioner 316 can move the cannula 304in the first direction and/or the second direction relative to thepipetting probe 302.

To determine a position of the cannula 304 relative to the container 306(e.g., an upper surface or cap of the container 306), the examplepipetting system 301 employs one or more sensors 320. In some examples,the sensors 320 (e.g., optical sensors, infrared sensors, etc.)determine an amount or distance the cannula 304 has moved relative to anupper surface or end of the container 306. In some examples, the sensors320 detect or measure a distance between an end of the cannula and theupper end of the container 306 (e.g., a closed container). In someexamples, the sensors 320 detect the presence of the container 306and/or an upper surface of the container 306. In some such examples, thesensors 320 sense when the cannula 304 engages and/or pierces the uppersurface (e.g., a septum or cap) of the container 306. In some examples,the sensors 320 determine when the cannula 304 has penetrated thecontainer 306 and is positioned in the cavity at a predetermineddistance relative to the upper surface of the container 306.

To control the operation of the probe positioner 312 via the first motor314 and the cannula positioner 316 via the second motor 318, the examplepipetting system 301 of the illustrated example employs a controller322. For example, the controller 322 commands the second motor 318 tomove the cannula 304 in the first direction and/or the second directionvia the cannula positioner 316, and the controller 322 commands thefirst motor 314 to move the pipetting probe 302 in the first directionand/or the second direction via the probe positioner 312. To provideinformation regarding a position of the pipetting probe 302 and/or aposition of the cannula 304 relative to the container 306 (e.g., anupper surface of the container 306), the pipetting system 301 of theillustrated example employs a position determiner 324. The positiondeterminer 324 may receive one or more signals from sensors 320providing feedback information regarding a position of the pipettingprobe 302 and/or a position of the cannula 304 relative to the container306. For example, the position determiner 324 determines a position ofthe pipetting probe 302, a position of the cannula 304, and/or aposition of the container 306 and communicates this information to thecontroller 322. The controller 322, in turn, controls the movement ofthe pipetting probe 302 and/or the cannula 304 based on the positioninformation provided by the position determiner 324. For example, thecontroller 322 may prevent or stop operation of the first motor 314until the position determiner 324 determines that the cannula 304 haspierced the container 306 and/or is positioned inside the container 306.After the position determiner 324 determines that the cannula 304 isinside the container 306, the controller 322 may cause or command thefirst motor 314 to operate the probe positioner 312 and cause the probe302 to move inside the container 306 (e.g., via an access opening of thecannula 304). In some examples, the controller 322 commands the secondmotor 318 to stop movement of the cannula 304 when the positiondeterminer 324 determines that the cannula 304 is inside a cavity of thecontainer 306.

To determine when the pipetting probe 302 engages a fluid (e.g., abiological sample or a reagent) in the container 306, the pipettingsystem 301 of the illustrated example employs the liquid level sensingsystem 300. The liquid level sensing system 300 of the illustratedexample includes a processor 326, a signal generator 328, a signalanalyzer 330, and an input/output interface 332 that are communicativelycoupled via a field bus 334. The signal analyzer 330 of the illustratedexample includes an amplitude detector 336 and a rate of change ofamplitude detector 338. In some examples, however, the signal analyzer330 of the illustrated example includes the amplitude detector 336. Theliquid level sensing system 300 is communicatively coupled to thecontroller 322 via a wired and/or wireless communication channel orcommunication link 340.

In the illustrated example, the signal generator 328 electricallyenergizes the pipetting probe 302 and the cannula 304 with anelectrically phase controlled signal. In some examples, the signalgenerator 328 of the illustrated example electrically energizes thepipetting probe 302 and the cannula 304 upon movement of the pipettingprobe 302 via the probe positioner 312 and/or the cannula 304 via thecannula positioner 316. For example, the controller 322 may communicateor command the signal generator 328 via the input/output interface 332and the communication link 340 to electrically energize the pipettingprobe 302 and/or the cannula 304. In some examples, the controller 322communicates or commands the signal generator 328 to electricallyenergize the pipetting probe 302 and/or the cannula 304 after at least aportion of the cannula 304 is positioned or disposed inside (e.g., haspierced) the container 306 and prior to movement of the pipetting probe302 toward the container 306.

The signal generator 328 of the illustrated example electricallyenergizes the pipetting probe 302 to provide a first signal 342 to thepipetting probe 302 and electrically energizes the cannula 304 toprovide a second signal 344 to the cannula 304. For example, each of thepipetting probe 302 and the cannula 304 emits or transmits a radiofrequency signal when the first signal 342 is provided to the pipettingprobe 302 and the second signal 344 is provided to the cannula 304. Insome examples, the first signal 342 provided to the pipetting probe 302is electrically in-phase with the second signal 344 provided to thecannula 304. In some examples, the first signal 342 may be identical tothe second signal 344. For example, the first signal 342 of thepipetting probe 302 and the second signal 344 of the cannula 304 mayeach emit a signal having a frequency of approximately 125 kHz (e.g.,plus or minus 10%). In some examples, the first signal 342 and/or thesecond signal 344 may have a frequency between approximately 0.3 Hz (oralternatively a DC potential) and 300 GHz. In some examples, the firstsignal 342 may be shifted out of phase (e.g., 90 degree phase shift, a45 degree phase shift, or any other phase shift value) relative to thesecond signal 344. For example, the first signal 342 may lag the secondsignal 344 by a predetermined phase shift. In some examples, the firstsignal 342 and/or the second signal 344 may have a waveform including asine wave, a square wave, a triangular wave, a sawtooth wave, etc. Insome examples, the signal generator 328 may include a first signalgenerator to generate the first signal 342 to the pipetting probe 302and a second signal generator to generate the second signal 344 to thecannula 304. The signal generator 328 of the illustrated example is alow impedance driver signal source.

In some examples, the signal generator 328 and, more generally, theexample liquid level sensing system 300 may include a phase-lock loopcontrol system for frequency generation, improved frequency stabilityand alignment between the first signal 342 and the second signal 344.For example, the phase-lock loop circuit maintains a relationshipbetween the signal of the cannula 304 and the signal of the pipettingprobe 302. In some examples, the phase-lock loop circuit maintains theelectrically phase controlled electrical potential between the signal ofthe cannula 304 and the signal of the pipetting probe 302. In someexamples, a phase-lock loop circuit may include a voltage-controlledoscillator, a phase detector, a low-pass filter, a variable-frequencyoscillator and a feedback that may include a frequency divider.

The liquid level sensing system 300 of the illustrated example detectswhen the pipetting probe 302 contacts a fluid (e.g., a liquid) inside acavity of the container 306. To determine when the pipetting probe 302contacts the fluid in the container 306, the example liquid levelsensing system 300 employs the signal analyzer 330. More specifically,as the pipetting probe 302 moves through the cannula 304 and/or insidethe cavity of the container 306 and relative to the liquid in thecontainer 306, the liquid level sensing system 300 detects changes inthe signal (e.g., the near-radio frequency (RF) signal) that is radiatedby the pipetting probe 302 and received by an antenna 346 positionedadjacent the container 306 (e.g., an antenna or a plurality of antennaspositioned adjacent the rotating carousel of FIG. 2 or adjacent thecontainer 306). The antenna 346 of the illustrated example iscommunicatively coupled to the signal analyzer 330 via the input/outputinterface 332 to transmit the received signal to the signal analyzer330. For example, the signal analyzer 330 continually monitors thesignal of the pipetting probe 302 as the pipetting probe 302 movesthrough an air-filled portion (e.g., a non-liquid filled portion) of thecontainer 306 above the liquid and detects a change in signal and a rateof change in signal to detect the signal of the pipetting probe 302 whenthe pipetting probe 302 contacts the liquid in the container 306. Thesignal analyzer 330 (e.g., via a comparator) detects a change in thesignal in response to the pipetting probe 302 contacting the liquid inthe container 306 compared to the signal emitted by the pipetting probe302 when the pipetting probe 302 is moving through the air-filledportion of the container 306 above the liquid (e.g., not in contact withthe liquid 400).

More specifically, the amplitude detector 336 detects a change in theamplitude of the signal received by the antenna 346 as the pipettingprobe 302 moves relative to the cannula 304 and/or the container 306.The rate of change of amplitude detector 338 detects a rate of signalchange received by the antenna 346 as the pipetting probe 302 movesthrough the air-filled portion towards the liquid filled portion. Forexample, both the amplitude detector 336 and the rate of change ofamplitude detector 338 detect a change in the amplitude of the signalreceived by the antenna 346 as the pipetting probe 302 moves through theair (e.g., not in engagement with liquid in the container 306) and whenthe pipetting probe 302 comes into direct engagement with liquid in thecontainer 306. The example signal analyzer 330 determines the presenceof liquid when both the amplitude detector 336 and the rate of amplitudedetector 338 receive a signal indicative of the pipetting probe 302coming into contact with the liquid. Basing liquid detections on bothsignal amplitude and rate of change of signal amplitude reduces thenumber of false or failed liquid detections. However, as the pipettingprobe 302 contacts liquid in the container 306, the amplitude of thesignal generated by the pipetting probe 302 increases or, in otherwords, has a positive slope. Thus, for a given frequency of, forexample, 125 kHz, the amplitude of the signal received by the antenna346 may be greater than an amplitude of a system noise envelope when thepipetting probe 302 engages the liquid. The amplitude detector 336detects a change in the amplitude of the detected signal as thepipetting probe 302 moves relative to the cannula 304 and/or thecontainer 306. To prevent false detections, the rate of change ofamplitude detector 338 detects a change in the slope between theamplitude of the signal received by the antenna 346 and the slope of thesystem noise envelope. In this manner, if the slope of the detectedchange of amplitude is not greater than a threshold, the rate of changeof amplitude detector 338 determines that the pipetting probe 302 hasnot contacted the liquid. If the slope is greater than a threshold, therate of change of amplitude detector 338 determines that the pipettingprobe 302 contacted the liquid. In some examples, the signal analyzerdoes not include the rate of change of amplitude detector 338 andinstead only detects liquid when the amplitude detector 336 detects achange in the amplitude of a detected signal.

To remove or aspirate a volume of fluid from the container 306 when theliquid level sensing system 300 determines that the pipetting probe 302is in contact with the liquid in the container 306, the pipetting system301 of the illustrated example employs a pump 348 (e.g., a syringe). Forexample, the liquid level sensing system 300 may be configured to send asignal to the controller 322 to activate the pump 348. The controller322 may command the first motor 314 and the second motor 318 to operatethe probe positioner 312 and the cannula positioner 316 to remove thepipetting probe 302 and the cannula 304 from the container 306 after anamount of fluid is aspirated by the pipetting probe 302.

The liquid level sensing system 300 enables the energized pipettingprobe 302 to be positioned through a channel or opening of the energizedpiercing cannula 304 at an electrically phase controlled electricalpotential (e.g., similar or equal frequency, controlled out of phaseshift frequency, etc.) without electrical impediment of the signalemitted or transmitted by the pipetting probe 302 as the pipetting probe302 makes coordinated contact with liquid in the container 306 whilebeing adjacent (e.g., passing through) the cannula 304. As noted above,a phase-lock loop control system may be employed for signal phaseintegrity and/or jitter control.

While an example manner of implementing the pipetting system 301 isillustrated in FIG. 3, one or more of the elements, processes and/ordevices illustrated in FIG. 3 may be combined, divided, re-arranged,omitted, eliminated and/or implemented in any other way. Further, theexample liquid level sensing apparatus 300, the example probe positioner312, the example cannula positioner 316, the example controller 322, theexample positioner determiner 324, the example processor 326, theexample signal generator 328, the example signal analyzer 330, theexample amplitude detector 336, the example rate of change of amplitudedetector 338, the example input/output interface 332 and/or, moregenerally, the example pipetting system 301 of FIG. 3 may be implementedby hardware, software, firmware and/or any combination of hardware,software and/or firmware. Thus, for example, any of the example liquidlevel sensing apparatus 300, the example probe positioner 312, theexample cannula positioner 316, the example controller 322, the examplepositioner determiner 324, the example processor 326, the example signalgenerator 328, the example signal analyzer 330, the example amplitudedetector 336, the example rate of change of amplitude detector 338, theexample input/output interface 332 and/or, more generally, the examplepipetting system 301 of FIG. 3 could be implemented by one or moreanalog or digital circuit(s), logic circuits, programmable processor(s),application specific integrated circuit(s) (ASIC(s)), programmable logicdevice(s) (PLD(s)) and/or field programmable logic device(s) (FPLD(s)).When reading any of the apparatus or system claims of this patent tocover a purely software and/or firmware implementation, at least one ofthe example liquid level sensing apparatus 300, the example probepositioner 312, the example cannula positioner 316, the examplecontroller 322, the example positioner determiner 324, the exampleprocessor 326, the example signal generator 328, the example signalanalyzer 330, the example amplitude detector 336, the example rate ofchange of amplitude detector 338, the example input/output interface 332and/or, more generally, the example pipetting system 301 of FIG. 3is/are hereby expressly defined to include a non-transitory computerreadable storage device or storage disk such as a memory, a digitalversatile disk (DVD), a compact disk (CD), a Blu-ray disk, etc.including the software and/or firmware. Further still, the examplepipetting system 301 of FIG. 3 may include one or more elements,processes and/or devices in addition to, or instead of, thoseillustrated in FIG. 3, and/or may include more than one of any or all ofthe illustrated elements, processes and devices.

FIG. 4 is a schematic illustration of the example pipetting system 301and the example liquid level sensing system 300 of FIG. 3 to detect orsense a level of a liquid 400 in the container 306 via the pipettingprobe 302 when using the cannula 304 to pierce the container 306. Theliquid level sensing system 300 includes a circuit board 402 (e.g., aprinted circuit board) that includes the signal generator 328 to provideor generate the first signal 342 to the pipetting probe 302 and thesecond signal 344 to the cannula 304. In some examples, the circuitboard 402 is configured to receive approximately +5 Volts.

The first signal 342 generated by the signal generator 328 istransmitted to the pipetting probe 302 via a connector or first cable408 (e.g., a coax cable). Similarly, the second signal 344 generated bythe signal generator 328 is transmitted to the cannula 304 via a secondconnector or second cable 410 (e.g., a coax cable). In some examples, aphase-locked loop control system may be employed for frequencygeneration, improved frequency stability and alignment between the firstsignal 342 and the second signal 344.

In some examples, neither the pipetting probe 302 nor the cannula 304are grounded. In some examples, both the pipetting probe 302 and thecannula 304 are grounded. The antenna 346 of the illustrated example iscommunicatively coupled to the liquid level sensing system 300 via aconnector or cable 412 (e.g., a coaxial cable). The antenna 346 of theillustrated example is grounded via a ground 414. The antenna 346 ismounted or positioned in a stationary position beneath an area whereliquid sensing is desired (e.g., beneath the container 306). In someexamples, the antenna 346 includes a plurality of antennas positionedbelow the rotating carousel 204 of the analytical system 100 of FIG. 1.The antenna 346 transmits the received signal from the pipetting probe302 to the liquid level sensing system 300 via the cable 412. Theexample liquid level sensing system 300 of the illustrated example mayemploy a shield circuit 416 as described in greater detail in connectionwith FIG. 10.

FIG. 5 illustrates the pipetting system 301 in a first position 500(e.g., a stationary or initial position). Referring to FIG. 5, thecannula 304 of the illustrated example includes a body 502 (e.g., acylindrical body) having a first end 504 and a second end 506 oppositethe first end 504. The cannula 304 includes a channel or opening 508 toform an access or passageway 510 between the first end 504 and secondend 506 (e.g., between an exterior of the container 306 and an interiorof the container 306). The first end 504 of the cannula 304 of theillustrated example includes a cannula tip 512 (e.g., an angled tip) tofacilitate piercing or puncturing a seal 514 (e.g., a cap) positioned ata first end 516 of the container 306 to provide access to a cavity 518of the container 306 (e.g., a sealed container). The seal 514 of theillustrated example may include a septum that may be pierced (e.g.,repeatedly pierced) by the cannula 304. The pipetting probe 302 of theillustrated example is a hollow tube that passes through the passageway510 of the cannula 304. The cannula 304 and the pipetting probe 302 ofthe illustrated example are composed of electrically conductive materialor combination of materials. For example, the cannula 304 and/or thepipetting probe 302 may be composed of aluminum, stainless steel, analloy and/or any other electrically conductive material(s). The antenna346 is positioned adjacent (e.g., underneath) a second end 520 of thecontainer 306 opposite the first end 516. In the first position 500 ofFIG. 5, the pipetting probe 302 and the cannula 304 are spaced away(e.g., vertically spaced) from the container 306 such that neither thecannula 304 nor the pipetting probe 302 are in direct contact with theseal 514 and/or the container 306. Further, in the example firstposition 500 of FIG. 5, the first signal 342 and the second signal 344is not provided to the pipetting probe 302 and cannula 304.

FIG. 6 illustrates the pipetting system 301 in a second position 600.For example, in the second position 600 of FIG. 6, the liquid levelsensing system 300 and/or the pipetting system 301 received a command toobtain a sample of liquid 400 from the cavity 518 of the container 306.In response to receiving the command, the signal generator 328 providesthe first signal 342 to the pipetting probe 302 and the second signal344 to the cannula 304. The pipetting probe 302 of the illustratedexample is composed of an electrically conductive material to enable thepipetting probe 302 to emit the first signal 342 and/or the cannula 304of the illustrated example is composed of an electrically conductivematerial to enable the cannula 304 to emit the second signal 344. Whenelectrically charged or energized with the first signal 342, thepipetting probe 302 emits a first electrical field 602 relative to alongitudinal axis 604 of the pipetting probe 302. When the cannula 304is electrically charged or energized with the second signal 344, thecannula 304 emits a second electrical field 606 relative to alongitudinal axis 608 of the cannula 304.

The first signal 342 radiated by the probe traverses or radiates acrossthe air space between the pipetting probe 302 and the antenna 346. Thefirst signal 342 is coupled from the pipetting probe 302 to the antenna346 primarily by the first electrical field 602. Because the firstelectrical field 602 is actually part of an electromagnetic fieldradiating from the pipetting probe 302, the liquid level sensing system300 may also be referred to as an “RF” (radio frequency) sensing system,although in some examples an actual frequency employed by the firstsignal 342 (e.g., 125 kHz) may be several octaves below standard radiofrequencies. When the pipetting probe 302 and the cannula 304 arepositioned in the air, the antenna 346 receives a relatively weak orsmall signal (e.g., a null) from the first electrical field 602 alongthe extension of the longitudinal axis 604 of the pipetting probe 302and/or the second electrical field 606 along the extension of thelongitudinal axis 608 of the cannula 304.

Further, because the cannula 304 of the illustrated example radiates thesecond electrical field 606 provided by the second signal 344 (e.g.,which may be identical or substantially similar to the first signal342), the cannula 304 when composed of an electrically conductivematerial does not interfere or degrade the first electrical field 602and/or the first signal 342 emitted or transmitted by the pipettingprobe 302 when the pipetting probe 302 passes through the passageway 510or is otherwise positioned adjacent the cannula 304. Absent the secondsignal 344, the cannula 304, when composed of an electrically conductivematerial, may degrade or otherwise interfere with the first signal 342radiated by the pipetting probe 302 when the pipetting probe 302 passesthrough the passageway 510 or is positioned adjacent the cannula 304.Electrically grounding only the cannula 304 would not help preventdegradation of the first signal 342 because an electrically groundedcannula 304 attracts or shields the first signal 342 radiated by thepipetting probe 302 instead of enabling the first signal 342 to radiatetoward the antenna 346 along the longitudinal axis 604 of the pipettingprobe 302 if the pipetting probe 302 is not also grounded. Thus, in someexamples, neither the pipetting probe 302 nor the cannula 304 aregrounded. In some examples, both the pipetting probe 302 and the cannula304 is grounded or at a DC potential.

When the liquid level sensing system 300 receives a command to obtain asample of the liquid 400 in the container 306, the controller 322commands the second motor 318 to operate the cannula positioner 316. Toposition the cannula 304 in the cavity 518 of the container 306, theposition determiner 324 receives positional information representativeof a position of the cannula 304 relative to the container 306 from thesensors 320. For example, the position determiner 324 determines theposition of the container 306 relative to the cannula 304 and commandsthe cannula positioner 316 to move in a first direction (e.g.,horizontally) via the second motor 318 to align with the container 306.The sensors 320 detects the position of the seal 514, and the controller322 commands the second motor 318 to move in a second direction (e.g.,vertically) toward the seal 514 via the cannula positioner 316. Thesensors 320 detect when the cannula 304 is immediately adjacent (e.g.,in direct contact with) an upper surface 614 of the seal 514 andcommunicates this information to the controller 322. The controller 322may command or cause the second motor 318 to stop after a certain periodof time lapses from the time of detection of the cannula 304 beingadjacent the upper surface 614 of the seal 514. For example, theposition determiner 324 may instruct the controller 322 to command thesecond motor 318 to stop after 3 milliseconds from the time the positiondeterminer 324 detects the cannula tip 512 being in direct contact withthe upper surface 614 of the seal 514 to ensure that the cannula tip 512pierces the seal 514 and at least partially enters the cavity 518 of thecontainer 306. Thus, the cannula tip 512 of the cannula 304 is at leastpartially positioned in the cavity 518 or the container 306 when thecannula 304 pierces the container 306. In some examples, the sensors 320may detect when the cannula 304 has pierced through the seal 514 and ispositioned in the cavity 518. After the cannula 304 has pierced the seal514, the controller 322 commands or causes the second motor 318 to stop(e.g., remove power to the second motor 318).

FIG. 7 illustrates the pipetting system 301 in a third position 700. Inthe third position 700 of FIG. 7, the pipetting probe 302 is positionedin the passageway 510 of the cannula 304. For example, the controller322 may command or cause the first motor 314 to operate to move thepipetting probe 302 (e.g., vertically) toward the container 306 via theprobe positioner 312. As shown in FIG. 7, although the cannula 304 iscomposed of a metallic or electrically conductive material, the firstelectrical field 602 generated by the first signal 342 through thepipetting probe 302 is not affected by the cannula 304 because thesecond signal 344 is radiating the second electrical field 606 throughthe cannula 304. In some instances, the second signal 344 of the cannula304 may prevent degradation of the first signal 342 emitted by thepipetting probe 302.

FIG. 8 illustrates the pipetting system 301 in a fourth position 800. Inthe example fourth position 800 of FIG. 8, the pipetting probe 302contacts the liquid 400 in the cavity 518 of the container 306 via thepassageway 510 provided by the cannula 304. In particular, the liquidlevel sensing system 300 determines when the pipetting probe 302contacts the liquid 400 and provides a signal to the controller 322 tocommand or cause the first motor 314 to stop (e.g., remove power to thefirst motor 314). In operation, when the pipetting probe 302 is loweredin the cavity 518 of the container 306 and contacts the liquid 400, thefirst signal 342 from the pipetting probe 302 to the antenna 346increases or is greater (e.g., a greater intensity) than a signalreceived by the antenna 346 from the pipetting probe 302 when thepipetting probe 302 is in air (e.g., not in contact with the liquid 400in the cavity 518). The signal increases because the liquid 400 in thecontainer 306, in effect, propagates the signal transmitted by thepipetting probe 302 by directing the electromagnetic field of thepipetting probe 302 toward the receiving antenna 346. In other words,the amplitude of the received first signal 342 is greater when thepipetting probe 302 contacts the liquid 400 than when the pipettingprobe 302 is not in contact with the liquid 400. The antenna 346receives a stronger signal (e.g., a signal with a greater amplitude)transmitted by the pipetting probe 302 when the pipetting probe 302 isin contact with the liquid 400 and communicates the signal to the signalanalyzer 330.

In turn, signal analyzer 330, via the amplitude detector 336 and therate of change of amplitude detector 338, determines if the pipettingprobe 302 contacts the liquid 400. As noted above, the amplitudedetector 338 detects a spike or change in amplitude provided by thefirst signal 342 when compared to, for example, a system noise envelope,and amplitude of the first signal 342 when the pipetting probe 302 isnot in direct contact with the liquid 400, etc. The rate of change ofamplitude detector 338 prevents false positives by analyzing a slope ofa curve of the amplitude detected by the amplitude detector 338 todetermine if the detected slope is greater than a threshold. The rate ofchange of amplitude detector 338 detects whether the slope of theamplitude detected by the amplitude detector 336 is greater than athreshold and communicates this result to the signal analyzer 330. Thesignal analyzer 330 determines that the pipetting probe 302 hascontacted the liquid 400 based on the signal provided by the antenna 346when an amplitude is detected and a rate of change of the amplitudedetected is greater than a threshold. As a result, the example liquidlevel sensing system 300 detects contact with the liquid 400 upon a tip802 of the pipetting probe 302 contacting the liquid 400. For example,when the pipetting probe 302 contacts the liquid 400 in the container306, a signal propagates through the liquid 400. The signal to thecannula 304 helps prevent degradation of the signal that enters orbroadcasted by the pipetting probe 302 when, for example, the cannula304 is composed of an electrically conductive material. Thus, the secondsignal 344 to the cannula 304 helps promote the first signal 312 throughthe pipetting probe 302 to reach the antenna 346.

When the signal analyzer 330 determines that the pipetting probe 302 isin contact with the liquid 400 (e.g., using the amplitude detector 336and/or the rate of change of amplitude detector 338), the signalanalyzer 330 instructs the controller 322 to stop operation of the firstmotor 314 (e.g., remove power to the first motor 314). The controller322 instructs the pump 348 to activate to enable a sample of the liquid400 in the cavity 518 of the container 306 to be aspirated in the hollowbody of the pipetting probe 302. Once the pump 348 has activated toobtain the sample, the controller 322 commands the first motor 314 tomove the pipetting probe 302 via the probe positioner 312 away from theliquid 400 and/or the container 306. After the pipetting probe 302 isremoved from the container 306 and/or the passageway 510 of the cannula304, the controller 322 commands the second motor 318 to move thecannula 304 via the cannula positioner 316 away from the container 306so that the cannula 304 is removed from the cavity 518 and/or spacedfrom the upper surface 614 of the seal 514.

Alternatively, as noted above, the example pipetting system 301 may beconfigured with other types of signals to provide liquid leveldetection. For example, the pipetting system 301 may be configured witha digital signal to sense when the pipetting probe 302 contacts theliquid 400 (e.g., using a DC potential). For example, the pipettingprobe 302 and the cannula 304 may be provided with substantially thesame voltage. In some such examples, the signal generator 328 may beconfigured to provide a voltage to the pipetting probe 302 and thecannula 304 representative of the first signal 342 and the second signal344, respectively. For example, the pipetting probe 302 emits anelectrostatic field potential (e.g., the first signal 342) that issubstantially similar to an electrostatic field potential (e.g., thesecond signal 344) emitted by the cannula 304 as the pipetting probe 302passes through the cannula 304 because the same voltage is applied tothe cannula 304 and the pipetting probe 302. Thus, in operation, thevoltage or the first signal 342 applied to the pipetting probe 302 willnot be affected when the pipetting probe 302 passes through the cannula304 and/or through the air-filled portion of the container 306. When thepipetting probe 302 contacts the liquid 400, the electrostatic fieldemitted by the pipetting probe 302 shifts or changes (e.g., increases inamplitude). The change in the electrostatic field is sensed or receivedby the antenna 346. For example, a change in the DC potential of thefirst signal 342 is detected when the pipetting probe 302 moves throughthe air-filled portion (e.g., a non-liquid filled portion) of thecontainer 306 above the liquid and when the pipetting probe 302 contactsthe liquid 400. In turn, the signal analyzer 330, via the amplitudedetector 336 and/or the rate of change of amplitude detector 338,determines if the pipetting probe 302 contacts the liquid 400. Forexample, to determine when the pipetting probe 302 directly engages orcontacts the liquid 400, the signal analyzer 330 detects a shift orchange (e.g., in amplitude) of the electrostatic field potentialprovided by the first signal 342 of the pipetting probe 302 whencompared to, for example, (e.g., an amplitude of) the electrostaticfield potential provided by the first signal 342 when the pipettingprobe 302 is not in direct contact with the liquid 400.

A flowchart 900 representative of example machine readable instructionsfor implementing the liquid level sensing system 300 and/or thepipetting system 301 of FIGS. 3-8 is shown in FIG. 9. In this example,the machine readable instructions comprise a program for execution by aprocessor such as the processor 1012 shown in the example processorplatform 1000 discussed below in connection with FIG. 10. The programmay be embodied in software stored on a non-transitory computer readablestorage medium such as a CD-ROM, a floppy disk, a hard drive, a digitalversatile disk (DVD), a Blu-ray disk, or a memory associated with theprocessor 1012, but the entire program and/or parts thereof couldalternatively be executed by a device other than the processor 1012and/or embodied in firmware or dedicated hardware. Further, although theexample program is described with reference to the flowchart illustratedin FIG. 9, many other methods of implementing the example liquid levelsensing system 300 and/or the pipetting system 301 may alternatively beused. For example, the order of execution of the blocks may be changed,and/or some of the blocks described may be changed, eliminated, orcombined. Additionally or alternatively, any or all of the blocks may beimplemented by one or more hardware circuits (e.g., discrete and/orintegrated analog and/or digital circuitry, a Field Programmable GateArray (FPGA), an Application Specific Integrated circuit (ASIC), acomparator, an operational-amplifier (op-amp), a logic circuit, etc.)structured to perform the corresponding operation without executingsoftware or firmware.

As mentioned above, the example processes of FIG. 9 may be implementedusing coded instructions (e.g., computer and/or machine readableinstructions) stored on a non-transitory computer and/or machinereadable medium such as a hard disk drive, a flash memory, a read-onlymemory, a compact disk, a digital versatile disk, a cache, arandom-access memory and/or any other storage device or storage disk inwhich information is stored for any duration (e.g., for extended timeperiods, permanently, for brief instances, for temporarily buffering,and/or for caching of the information). As used herein, the termnon-transitory computer readable medium is expressly defined to includeany type of computer readable storage device and/or storage disk and toexclude propagating signals and to exclude transmission media.“Including” and “comprising” (and all forms and tenses thereof) are usedherein to be open ended terms. Thus, whenever a claim lists anythingfollowing any form of “include” or “comprise” (e.g., comprises,includes, comprising, including, etc.), it is to be understood thatadditional elements, terms, etc. may be present without falling outsidethe scope of the corresponding claim. As used herein, when the phrase“at least” is used as the transition term in a preamble of a claim, itis open-ended in the same manner as the term “comprising” and“including” are open ended.

The example program of FIG. 9 includes providing a first signal (e.g.the RF signal) to a probe to cause the probe to generate the firstelectrical field (block 902). For example, the signal generator 328 maybe instructed or commanded to apply the first signal 342 to thepipetting probe 302 when the controller 322 receives a command to obtaina sample of liquid 400 from the cavity 518 of the container 306.

The example program 900 also includes providing a second signal (e.g. aRF signal) to a cannula to cause the cannula to generate a secondelectrical field (block 904). In some examples, the signal generator 328provides the second signal 304 to the cannula 344 to cause the cannula304 to generate the second electrical field 606. In some examples, thefirst signal 342 provided to the pipetting probe 302 by the signalgenerator 328 is substantially the same (e.g., within plus or minus 10%)or identical to the second signal 344 provided to the cannula 304 by thesignal generator 328. In some examples, the first signal 342 provided bythe signal generator 328 is shifted out of phase relative to the secondsignal 344 generated by the signal generator 328.

The example program 900 includes causing a cannula to pierce a seal of acontainer to provide an access to a liquid in the container (block 906).For example, the controller 322 may cause or command the second motor318 to move the cannula 304 toward the container 306 via the cannulapositioner 316 until the cannula tip 512 pierces or passes through theseal 514 and into the cavity 518 of the container 306.

The example program 900 includes moving a probe through a passageway ofthe cannula and into the cavity of the container (block 908). Forexample, the controller 322 may cause or command the first motor 314 tomove the pipetting probe 302 relative to the container 306 via the probepositioner 312 and toward the liquid 400 in the container 306 throughthe passageway 510 of the cannula 304.

The example program 900 includes receiving, via an antenna, the firstsignal generated by the probe as the probe moves into the cavity of thecontainer (block 910). For example, the first signal 342 applied to thepipetting probe 302 generates the first electrical field 602 that isdetected or received by the antenna 346 as the pipetting probe 302 movesinto the cavity 518.

A signal analyzer detects a change in the first signal (block 912). Thesignal analyzer determines if the first signal is greater than athreshold (block 914). For example, the signal analyzer 330 employs theamplitude detector 336 to detect a change (e.g., an increase ordecrease) in an amplitude of the first signal 342 and the rate of changeof amplitude detector 338 to detect a rate of change (e.g., a rate ofincrease or decrease) of the detected first signal 342. For example, theamplitude detector 336 determines an amplitude of the first signal 342compared to, for example, a slope of a system noise envelope of theanalytical system 100. If the amplitude is greater than a threshold(e.g., a detected magnitude of the first signal 342 being greater than10 percent of a magnitude of the slope of the system noise envelopecurve), then the amplitude detector 336 determines that an amplitudechange has occurred. When an amplitude change has occurred, the rate ofchange of amplitude detector 338 detects if a slope between the curve ofthe system noise envelope and a peak of the amplitude detected when thechange occurred is greater than a threshold.

If the signal analyzer determines that the change in the detected firstsignal is not greater than a threshold at block 914, then the processreturns to block 912. If the signal analyzer determines that the changein the detected first signal is greater than the threshold at block 914,the signal analyzer determines that the probe is in contact with theliquid in the container (block 916). Thus, the liquid level sensingsystem 300 of the illustrated example determination that the pipettingprobe 302 engages the liquid 400 is based on detection of both a signalamplitude detected by the amplitude detector 336 and a rate of change ofsignal amplitude detected by the rate of change of amplitude detector338. In other words, it is determined that the pipetting probe 302 hascontacted the liquid 400 when both the signal amplitude and the rate ofsignal change indicate that the amplitude change and rate of change hasoccurred.

The controller stops movement of the probe when the probe is determinedto be in contact (e.g., direct contact) with the liquid in the container(block 918). For example, the controller 322 commands or causes thefirst motor 314 to stop by removing power to the first motor 314.

A liquid sample from the container is then aspirated (block 920). Forexample, with the tip 802 of the pipetting probe 302 in the liquid 400after the first motor 314 is commanded to stop, the controller 322activates the pump 348 to aspirate a sample of the liquid 400 in thecontainer 306.

After the liquid is aspirated, the probe and the cannula are removedfrom the container (block 922). For example, the controller 322 commandsor causes the first motor 314 to operate to cause the pipetting probe302 to move away from the container 306 via the probe positioner 312 andthe controller commands or causes the second motor 318 to operate tocause the cannula 304 to move away from the container 306 via thecannula positioner 316.

The example liquid level sensing system 300 disclosed herein may be usedin any automated instrument where liquid level sensing is desired.

FIG. 10 is a block diagram of an example processor platform 1000 capableof executing the instructions of FIG. 9 to implement the liquid levelsensing system 300 or the pipetting system 301 of FIG. 3. The processorplatform 1000 can be, for example, a server, a personal computer, amobile device (e.g., a cell phone, a smart phone, a tablet such as aniPad™), a personal digital assistant (PDA), an Internet appliance or anyother type of computing device.

The processor platform 1000 of the illustrated example includes aprocessor 1012. The processor 1012 of the illustrated example ishardware. For example, the processor 1012 can be implemented by one ormore integrated circuits, logic circuits, microprocessors or controllersfrom any desired family or manufacturer. The hardware processor may be asemiconductor based (e.g., silicon based) device. In this example, theprocessor implements the example liquid level sensing apparatus 300, theexample probe positioner 312, the example cannula positioner 316, theexample controller 322, the example positioner determiner 324, theexample processor 326, the example signal generator 328, the examplesignal analyzer 330, the example amplitude detector 336, the examplerate of change of amplitude detector 338, the example input/outputinterface 332 and/or, more generally, the example pipetting system 301.

The processor 1012 of the illustrated example includes a local memory1013 (e.g., a cache). The processor 1012 of the illustrated example isin communication with a main memory including a volatile memory 1014 anda non-volatile memory 1016 via a bus 1018. The volatile memory 1014 maybe implemented by Synchronous Dynamic Random Access Memory (SDRAM),Dynamic Random Access Memory (DRAM), RAMBUS Dynamic Random Access Memory(RDRAM) and/or any other type of random access memory device. Thenon-volatile memory 1016 may be implemented by flash memory and/or anyother desired type of memory device. Access to the main memory 1014,1016 is controlled by a memory controller.

The processor platform 1000 of the illustrated example also includes aninterface circuit 1020. The interface circuit 1020 may be implemented byany type of interface standard, such as an Ethernet interface, auniversal serial bus (USB), and/or a PCI express interface.

In the illustrated example, one or more input devices 1022 are connectedto the interface circuit 1020. The input device(s) 1022 permit(s) a userto enter data and/or commands into the processor 1012. The inputdevice(s) can be implemented by, for example, an audio sensor, amicrophone, a camera (still or video), a keyboard, a button, a mouse, atouchscreen, a track-pad, a trackball, isopoint and/or a voicerecognition system.

One or more output devices 1024 are also connected to the interfacecircuit 1020 of the illustrated example. The output devices 1024 can beimplemented, for example, by display devices (e.g., a light emittingdiode (LED), an organic light emitting diode (OLED), a liquid crystaldisplay, a cathode ray tube display (CRT), a touchscreen, a tactileoutput device, a printer and/or speakers). The interface circuit 1020 ofthe illustrated example, thus, typically includes a graphics drivercard, a graphics driver chip and/or a graphics driver processor.

The interface circuit 1020 of the illustrated example also includes acommunication device such as a transmitter, a receiver, a transceiver, amodem and/or network interface card to facilitate exchange of data withexternal machines (e.g., computing devices of any kind) via a network1026 (e.g., an Ethernet connection, a digital subscriber line (DSL), atelephone line, coaxial cable, a cellular telephone system, etc.).

The processor platform 1000 of the illustrated example also includes oneor more mass storage devices 1028 for storing software and/or data.Examples of such mass storage devices 1028 include floppy disk drives,hard drive disks, compact disk drives, Blu-ray disk drives, RAIDsystems, and digital versatile disk (DVD) drives.

The coded instructions 1032 of FIG. 10 may be stored in the mass storagedevice 1028, in the volatile memory 1014, in the non-volatile memory1016, and/or on a removable tangible computer readable storage mediumsuch as a CD or DVD.

At least some of the aforementioned examples include one or morefeatures and/or benefits including, but not limited to, the following:

In some examples, an example liquid level sensing apparatus includes acannula defining a body having a tip and an access channel. The tip isto pierce a container. The cannula is to be at least partiallypositioned in the container when the tip pierces the container. In somesuch examples, a probe is to be positioned in the access channel. Insome such examples, a signal source is to electrically energize theprobe and the cannula to cause the probe to emit a first signal andcause the cannula to emit a second signal.

In some examples, the first signal is electrically phase controlledrelative to the second signal.

In some examples, the first and second signals are controlled viaphase-lock loop control system.

In some examples, an antenna is adjacent the container to detect atransmission of the first signal when the probe contacts a liquid in thecontainer and the probe is positioned through the access channel of thecannula.

In some examples, the cannula and the probe are composed of anelectrically conductive material.

In some examples, the first signal and the second signal are radiofrequency signals.

In some examples, the second signal emitted by the cannula is to preventdegradation of the first signal emitted by the probe when the probe ispositioned in the access channel of the cannula.

In some examples, the cannula does not interfere with the first signalemitted by the probe.

In some examples, neither the probe nor the cannula are electricallygrounded.

In some examples, the first signal is electrically in phase with thesecond signal.

In some examples, the first signal is electrically phase shifted fromthe second signal.

In some examples, both the probe and the cannula are electricallygrounded.

In some examples, at least one of the first signal or the second signalincludes a waveform having a sine wave, a square wave, a triangularwave, or a sawtooth wave.

In some examples, an example liquid level sensing apparatus includes acannula composed of a conductive material. In some such examples, thecannula is to pierce a seal of a container. In some such examples, thecannula is movable relative to the container in a first direction and asecond direction, where the first direction being different than thesecond direction. In some such examples, the cannula includes an openingpassing through a first end of the cannula and a second end of thecannula to define a passageway. In some such examples, the cannula is toemit a first signal when at least a portion of the cannula is positionedin a cavity of the container. In some such examples, a probe is composedof a conductive material. In some such examples, the probe is movablerelative to the cannula in the first direction and the second direction,where the probe to emit a second signal. In some such examples, theprobe is to pass through the passageway provided by the cannula toaspirate a sample from the container. In some such examples, a signalgenerator operatively couples to the cannula and the probe. In some suchexamples, the signal generator is to provide the first signal to thecannula and the second signal to the probe.

In some examples, the first signal is electrically in phase with thesecond signal.

In some examples, the first signal is electrically phase shifted fromthe second signal.

In some examples, neither the probe nor the cannula are electricallygrounded.

In some examples, both the probe and the cannula are electricallygrounded.

In some examples, an antenna is to receive the second signal of theprobe when the probe is inside the container and the passageway of thecannula.

In some examples, the cannula is to emit the first signal while theprobe is moving through the passageway of the cannula.

In some examples, the first signal emitted by the cannula is to preventdegradation of the second signal emitted by the probe when the probe ispositioned in the passageway of the cannula.

In some examples, a method for sensing liquid in a container includesproviding a first signal to a probe to cause the probe to emit a firstelectrical field. In some such examples, the method includes providing asecond signal to a cannula to cause the cannula to emit a secondelectrical field. In some such examples, the method includes moving thecannula to pierce a seal of a container to provide an access to a liquidin a cavity of the container. In some such examples, the method includesmoving the probe through a passageway of the cannula and into the cavityof the container while the probe emits the first electrical field andthe cannula emits the second electrical field.

In such examples, the method includes positioning an antenna adjacent abottom surface of the container, the antenna to receive the first signalemitted by the probe.

In some such examples, the method includes detecting a change in thefirst signal and determining if the detected change in the first signalis greater than a threshold.

In some such examples, the method includes stopping movement of theprobe when the detected change in the first signal is greater than thethreshold.

In some such examples, the method includes electrically groundingneither the probe nor the cannula.

In some such examples, the method includes electrically grounding boththe probe and the cannula.

In some examples, a non-transitory computer-readable medium includesinstructions that, when executed, cause a machine to: provide a firstsignal to a probe to cause the probe to emit a first electrical field;provide a second signal to a cannula to cause the cannula to emit asecond electrical field; move the cannula to pierce a seal of acontainer to provide an access to a liquid in a cavity of the container;and move the probe through a passageway of the cannula and into thecavity of the container while the probe emits the first electrical fieldand the cannula emits the second electrical field.

In some examples, the instructions when executed, further cause themachine to receive the first signal emitted by the probe via an antennapositioned adjacent a bottom surface of the container.

In some examples, the instructions when executed, further cause themachine to detect a change in the first signal and determine if thedetected change in the first signal is greater than a threshold.

In some examples, the instructions when executed, further cause themachine to stop movement of the probe when the detected change in thefirst signal is greater than the threshold.

Although certain example methods, apparatus and articles of manufacturehave been disclosed herein, the scope of coverage of this patent is notlimited thereto. On the contrary, this patent covers all methods,apparatus and articles of manufacture fairly falling within the scope ofthe claims of this patent.

What is claimed is:
 1. A method comprising: moving a cannula to pierce aseal of a container to provide access to a liquid in a cavity of thecontainer; moving a probe through a passageway of the cannula and intothe cavity of the container; and when the probe is at least partiallypositioned in the cannula: providing a first signal to the probe tocause the probe to emit a first electrical field; and providing a secondsignal to the cannula to cause the cannula to emit a second electricalfield.
 2. The method as defined by claim 1, further includingpositioning an antenna adjacent a bottom surface of the container, theantenna to receive the first signal emitted by the probe.
 3. The methodas defined by claim 1, further including: detecting a change in thefirst signal; and determining if the detected change in the first signalis greater than a threshold.
 4. The method as defined by claim 3,further including stopping movement of the probe when the detectedchange in the first signal is greater than the threshold.
 5. The methodas defined by claim 4, further including aspirating a portion of theliquid in the cavity of the container when the probe is positionedthrough the passageway of the cannula.
 6. The method as defined by claim1, further including electrically grounding neither the probe nor thecannula.
 7. The method as defined by claim 1, further includingelectrically grounding both the probe and the cannula.
 8. The method asdefined by claim 1, further including controlling the first and secondsignals via a phase-lock loop control system.
 9. The method as definedby claim 1, further including controlling the first signal to beelectrically in phase with the second signal.
 10. The method as definedby claim 1, further including controlling the first signal to beelectrically phase shifted with the second signal.
 11. A non-transitorycomputer-readable medium comprising instructions that, when executed,cause a machine to: move a cannula to pierce a seal of a container toprovide access to a liquid in a cavity of the container; move a probethrough a passageway of the cannula and into the cavity of thecontainer; and when the probe is at least partially positioned in thecannula: provide a first signal to the probe to cause the probe to emita first electrical field; and provide a second signal to the cannula tocause the cannula to emit a second electrical field.
 12. Thenon-transitory machine readable storage of claim 11, wherein whenexecuted, further cause the machine to receive the first signal emittedby the probe via an antenna positioned adjacent a bottom surface of thecontainer.
 13. The non-transitory machine readable storage of claim 11,wherein when executed, further cause the machine to: detect a change inthe first signal; and determine if the detected change in the firstsignal is greater than a threshold.
 14. The non-transitory machinereadable storage of claim 13, wherein when executed, further cause themachine to stop movement of the probe when the detected change in thefirst signal is greater than the threshold.
 15. The non-transitorymachine readable storage of claim 11, wherein when executed, furthercause the machine to aspirate a portion of the liquid in the cavity ofthe container when the probe is positioned through the passageway of thecannula.
 16. The non-transitory machine readable storage of claim 11,wherein when executed, further cause the first signal to be electricallyin phase with the second signal.
 17. The non-transitory machine readablestorage of claim 11, wherein when executed, further cause the firstsignal to be electrically phase shifted with the second signal.
 18. Aliquid sensing apparatus comprising: means for moving a means forpiercing a seal of a container to provide access to a liquid in a cavityof the container; means for moving a means for aspirating liquid througha passageway of the means for piercing the container and into the cavityof the container; and means for generating a first signal to the meansfor aspirating liquid to cause the means for aspirating liquid to emit afirst electrical field and a second signal to the means for piercing thecontainer to cause the means for piercing the container to emit a secondelectrical field when the means for aspirating liquid is at leastpartially positioned in the means for piercing the container.
 19. Theapparatus as defined by claim 18, further including means for receivingthe first signal emitted by the means for aspirating liquid, the meansfor receiving the first signal to be positioned adjacent a bottomsurface of the container.
 20. The apparatus as defined by claim 18,further including means for detecting a change in the first signal andmeans for determining if the detected change in the first signal isgreater than a threshold.